Vacri already said enough about import duties. No US state can or does impose duties.
US citizenship (as defined by the federal level) is a necessary condition for Texan citizenship. Texas can't grant any political rights to "Texan citizens" who are not US citizens.
Federal structure: Take a look at Germany or any other federal nation. Germany consists of 16 states that joined a union (that is known as Germany) and voluntarily ratified the constitution (well, enough of them ratified it and a one went along for the ride). The states are individual entities that have their own laws, police, and so on. Starting to see the similarities? Politically speaking, no US state is as sovereign as Germany. Not in theory and certainly not in practice. However, the single German states have a certain level of sovereignty just like US states have a certain level of sovereignty. It's not an absolute but a spectrum.
"Most folks here" are unaware of what you posted not because they don't know but because it's simply not true. Maybe you should do some research outside Wikipedia. Well, you can even start there: https://en.wikipedia.org/wiki/Federated_state I know that many people (including political scholars) in the US hold the view that the states are individual entities similar to entire nation states. Note that this view is shared by almost nobody outside the US.
Oh, and please don't respond to comments by editing your original post by the way. I could also spread out the university degrees of me and my conversation partners here but that does not change anything about facts. It's just a bad argument.
Also, we are all wrong on certain points given certain assumptions. For instance, given the assumption that a state is defined as a political entity with absolute sovereignty, the 50 U.S. States could not be termed states. I'm very well aware of that and probably should not have been authoring a response a bottle of Zinfandel into the awesome "Fortitude" series, from Amazon.
I was fortunate to be able to take a class, "The State and Sovereignty", with Richard Ashley, who more or less wrote the book (or paper) on post-modern or post-structural International Relations [1]. From another site: "Ashley is concerned with how concepts like the state, sovereignty, and war are rarely questioned as problematic in international politics (Ashley 1989: 302). If the state is the central unit of analysis in IR and yet it is rarely thoroughly examined, how accurate are the assumptions that realism and liberalism rest on?" [2]. My thesis for this class was on this exact topic. Titled "Sovereignty: A Non-Sequitur", I used a lot of words to reference a lot of other people who used even more word to call bs on the very concept of state sovereignty.
But, hey, that's what you get when you approach a complex topic in a blunt fashion. But let's not stop now, let's go to Wikipedia:
State (polity) := "A state is an organized political community living under a single system of government. Speakers of American English often use state and government as synonyms, with both words referring to an organized political group that exercises authority over a particular territory. States may or may not be sovereign. For instance, federated states that are members of a federal union have only partial sovereignty, but are, nonetheless, states." [3]
Federation := "A federation (from Latin: foedus, gen.: foederis, "covenant"), also known as a federal state, is a political entity characterized by a union of partially self-governing states or regions under a central (federal) government. " [4]
"The component states are in some sense sovereign, insofar as certain powers are reserved to them that may not be exercised by the central government. However, a federation is more than a mere loose alliance of independent states. The component states of a federation usually possess no powers in relation to foreign policy, and so they enjoy no independent status under international law. However, German Länder do have this power, which is beginning to be exercised on a European level." [4]
U.S. State := "A state of the United States of America is one of the 50 constituent political entities that shares its sovereignty with the United States federal government. Due to the shared sovereignty between each state and the federal government, Americans are citizens of both the federal republic and of the state in which they reside.[3] State citizenship and residency are flexible and no government approval is required to move between states, except for persons covered by certain types of court orders (e.g., paroled convicts and children of divorced spouses who are sharing custody)." [5]
German Länder (States of Germany) := "Though international relations including international treaties are primarily the responsibility of the federal level, the constituent states have certain limited powers in this area: in matters that affect them directly, the states defend their interests at the federal level through the Bundesrat (literally Federal Council, the upper house of the German Federal Parliament) and in areas where they have legislative authority they have limited powers to conclude international treaties 'with the consent of the federal government'." [6]
So, we have, at least as far as Wikipedia is concerned but surely others will say the issue is more complicated [0], that: federated states that are members of a federal union are indeed states, there is such a thing as state citizenship, and that states belonging to a Federation do enjoy independent status under international law.
Now, in practice, how do U.S. States feel about Trade agreements. Let me google that for you:
US citizenship (as defined by the federal level) is a necessary condition for Texan citizenship. Texas can't grant any political rights to "Texan citizens" who are not US citizens.
Federal structure: Take a look at Germany or any other federal nation. Germany consists of 16 states that joined a union (that is known as Germany) and voluntarily ratified the constitution (well, enough of them ratified it and a one went along for the ride). The states are individual entities that have their own laws, police, and so on. Starting to see the similarities? Politically speaking, no US state is as sovereign as Germany. Not in theory and certainly not in practice. However, the single German states have a certain level of sovereignty just like US states have a certain level of sovereignty. It's not an absolute but a spectrum.
"Most folks here" are unaware of what you posted not because they don't know but because it's simply not true. Maybe you should do some research outside Wikipedia. Well, you can even start there: https://en.wikipedia.org/wiki/Federated_state I know that many people (including political scholars) in the US hold the view that the states are individual entities similar to entire nation states. Note that this view is shared by almost nobody outside the US.
Oh, and please don't respond to comments by editing your original post by the way. I could also spread out the university degrees of me and my conversation partners here but that does not change anything about facts. It's just a bad argument.