After the qualifying year is verifiably complete and the corporate records support the structure, and after premises and capitalisation exist to describe. Filing earlier tends to create the shortfall it was meant to avoid.
Early filing is usually the wrong instinct
Commercial pressure pushes companies to file as soon as a plan exists, and the requirements push the other way. The qualifying year abroad is measured within the three years before the petition, so filing sooner means less of it has accrued. Premises must be secured for a new office and capitalisation must be real; the foreign organization must be doing business, while the new U.S.
office needs premises and the financial ability to commence business rather than existing operations. Each of those is easier to evidence a month later than a month earlier. The right question is not how soon the company can file but what the earliest date is on which every requirement is genuinely satisfied and documented.
Setting the commercial timetable from that date, rather than the reverse, avoids the common pattern of a filing that has to explain why several conditions were not quite met.