Before Brexit, EU resident's were all at IBUK who was introducing broker for IBLLC USA. In 2014 FATCA started and IRS sent tax data (name, surname, address, birth date, tax residency, TIN, account value on 31.12., gross interests, gross dividends, gross proceeds) to taxman of your country where you have tax residency.
Since 2017 we have CRS, and UK's HMRC︀ sent this data to taxman of your tax residency country, IRS also sent data via︁ FATCA.
At the end of 2020 we have all migrated to one of IB's branch︂ in EU (IBIE, IBLUX, IBCE) so taxman from Ireland/Luxembourg/Hungary will share data via CRS to︃ taxman of your country where you have tax residency. And IRS will also sent data︄ via FATCA.
There are some differences between CRS and FATCA (accounts > $50.000, every country︅ has specific bilateral agreement), but the main point for brokerage accounts is the same (account︆ value, gross interests, gross dividends, gross proceeds).
You can find more info on this in︇ Council Directive 2014/107/EU. It's a long and very detailed read.
https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32014L0107&from=EN
And one more thing,︈ back in 2014 and 2015 I didn't report dividends and interest from USA (few hundred︉ USD), my taxman sent me a letter in 2016 stating FATCA agreement and that IRS︊ sent them data that I had dividend and interest income in USA.