Can there be trade without or low tariffs between EU and USA or does USA first have to join the EU?
Yes. International trade agreements (usually bilateral), or agreements based on trade union (f.e. WTO) rulesets. States prefer bilateral agreements, because they can then be more 'tailored'.
(But also - within WTO rules, and within bilateral agrements, the 'stronger' fraction usually somewhat can 'impose' their ruleset. To a point of course, but it is a thing.)
This doesnt mean "no tariffs" ever, because as seen recently the US (or any other state) can one-sidedly announce, that they will put tariffs on certain goods, basically whenever (its a political tool - usually to signal 'we need to talk again'). But it means 'managed' trade relations, and usually - low necessity for tariffs.
The EU just established such an open trade agreement with the Mercosur states, and we (and the US and every other major trading block) has many of them throughout the world.
But open access to a market is more than that. F.e. same ruleset for safety regulations, same ruleset for norms and standards, ...
so a 'common market' is more than just no tariffs.
Trade agreements also are there to ensure 'investment safety'. Meaning - a company says - we want to mine your rare earth elements, we buy a license - which guarantees us x conditions and amounts of product. If then a protest comes along and destroys our operation for local interest reasons, you (state) have to reimburse us. Those are usually specific contracts, but to get them set up, you need a framework and thats usually fixed (set up) in WTO laws, or a bilateral trade agreement as well.
In the case with China, the chinese government currently accuses the US to use trade 'as a weapon' hurting (/containing
) the chinese economy on purpose.
And in that case, thats not wrong.
The US has an interest in slowing down chinese growth (Which they can do by controlling certain supply chains (f.e. because you have to pay for some stuff in USD (or some credit lines can be controlled by them, ...).
).
And/or because they impose tariffs (which slows income flow of lets say USD).
Companies ((/natural) monopolies) can do that as well btw. So if a large part of lets say batteries internationally is produced by Samsung and lets say germany wants to set up an electric car production, and then orders x million cells from Samsung, and then Samsung says - we can only deliver a fifth of your order in three years... It also slows down economic growth.
(And then Europe has battery summits, and founds a battery production industry, and then finds out, that the resources for battery production are mostly controlled by China - so now they have to source some of their own, and get into resource mining as well, and all of it is expensive - but not only having monopolies is good for production security, and so on and so forth..
)
And this is why - when canada arrests the daughter of the Huawai owner on behest of the US, stuff like this develops:
https://www.nytimes.com/2019/07/14/world/asia/china-canadian-arrested.html
edit: Sorry, should have edited the last post. Next time. I promise.