What is the best method for sending money from Croatia to the United States?

So a couple of things to be aware of:

1. Sending any form of walk-in money transfer service, you will not be allowed to send across US$ 25,000 into the US. This would immediately be reported via SAR (Suspicious Activity Report) and you are not allowed to exceed US$ 10,000 via a Money Service Business (walk-in exchange) first time around in a 30-day period.
2. Even Western Union would not be allowed to wire US$ 25,000 for 1st time customers (you can double check this with them).
3. This money would instantly be flagged by any system to bring it in - that's just the way the system works (assuming it is coming directly to your name and not a business account). Unless the money is illegal or tainted, you ought not to worry about this.
4. Your safest best is to have the amount wired across, this will probably cost your Croatian bank US$ 50 to US$ 75 to SWIFT wire transfer the amount.
5. If your funds are not in US Dollars at the Croatian end, converting them to USD, you will loose about 1% in Exchange parity (if done directly by the bank, as TT Charges are different from Open-Market rates).
6. Your wire could possibly be completed in as little as 2 days, but bet on 5-6 working days. Your bank will ask some questions as to the source of funds.

Other than what I have cited, this is a simple and a straightforward case of a Bank Wire Transfer. Any other method is simply not suggested.