There are many countries that make plastic model kits, e.g. Poland, Taiwan, Ukraine, South Korea, India... - not just China. All of them are affected now by US tariffs (exceptions are e.g. Russia, also producing plastic kits). And if these tariffs stay in place - all of these countries will impose similar tariffs on US products.

So imports into the US will be more expensive (for US customers, not for anyone outside the US) - and US exports will be more expensive for customers outside the US. So why move to the US, where you have a shrinking market and the worst export opportunities? It could still happen - but very unlikely to a significant extent.