When American companies do business on a multi-national basis, they have to comply with the business regulations in all of the countries where they do business. Anti-trust regulations are among those regulations. Anti-trust regulations are based upon day to day business activities of companies, unlike the internal corporate affairs of a company, which are only governed by the place of incorporation.
Companies like Adobe are multinational companies that do business in, and have large market shares in, many national markets. So, they are subject to the anti-trust regulations of the countries where they do business. Given that Adobe offered to pay $20 billion USD for Figma, it is safe to assume that it too is probably a pretty significant company, in terms of the relevant market shares, that does business in many countries, although it isn't as much of a household name.