The single-warehouse international model works when your US 3PL has strong international carrier relationships, can prepare customs documentation, and has same-day dispatch capability for international shipments.
Start with two or three international markets where your product already has demand signals — search volume on Amazon's international marketplaces, inbound traffic from specific countries in your Shopify analytics.
Test each market with a small batch before scaling. Ship 50 units via seller-fulfilled to the target country, measure conversion and return rates, and confirm customs clearance is straightforward before committing to local FC inventory.
Once you identify performing markets, consider transitioning top markets to in-country inventory (Amazon FBA in the local marketplace). Maintain the Florida warehouse as a prep and staging hub for mid-tier markets that do not justify in-country stock.