You can freely transfer any amount between your own accounts, and you do not have to worry about reporting requirements; the bank will handle whatever might be needed. No taxes are to be paid either.
That is true if the money is legally acquired, and previously reported as the IRS requires.
- if asked, you have to be able to proof that the money was legally acquired. 'Legally' here means legally according to US laws. If you cannot show where it came from, they might impound it.
- The IRS requires you to report annually any amount of money over 10,000 that you own or have control over in foreign countries (FBAR). if you did do so, you're fine. If you did not do that in previous years, you will probably get in trouble as this is considered potential tax evasion; they might give you a fine, impound the money, - or do nothing. You can voluntarily post-report it for previous years, I'd recommend you read up on how to do that.
Some of these consequences might sound really harsh, but they are laws to catch druglords washing their dirty money and such, not to bother normal people transferring inheritances, savings, or proceeds from home sales. If your money is clean, and you follow the rules, you have nothing to worry about.