Is it disadvantage if my first graduate job is outside of current country? [closed]

Experience is experience no matter where you go. Besides, working for someone cannot look bad on your CV unless you get fired for cause.

With that said, the countries you are thinking of moving to are not primarily-English-speaking countries. You will want to get at least some basic training in the primary language of the country you reside in.

Most European countries have a health system similar to how the US one is supposed to operate (health insurance is a common/basic thing like in the US, but is also really affordable, for instance), so while you may see similarities that give you cause for concern in that regard, it is not nearly as bad.

There are many recruitment agencies dedicated to prospective expats like yourself, so start your job search with a conversation with those companies.

Another big problem is going to be Brexit itself, assuming you are a UK citizen, as with Brexit will likely come the removal of your automatic right to work in an EU country. Not all of the EU countries have fully formed policies with what to do with British expats yet, but it seems the worst case scenario is you'll need to be able to get a work visa for most countries. If, on the off-chance you are eligible for a passport from another EU country, I would apply for one, as it will really save on headaches (and potential rejections due to such headaches) in the application process.