I really don't see us falling behind. We've sent several rovers and orbiters to Mars, and we've also sent many orbiters to the Moon recently. Just because we don't have a rover on the Moon doesn't mean we've fallen behind, not by a long shot. In fact, I'd say China still has a long way to go before they catch up.
If we were really that far ahead, we could whip up a moon rover of our own and beat them to the punch. We can't.