There's a big difference between a US company choosing to bid on acquisition of P&O's worldwide operations, and a US company capable of operating P&O's rather modest North American operations.
Surely you're not under the impression that P&O's North American operations constitute some kind of port-terminal-monolith. And surely you're not under the impression that the US is devoid of capable, and indeed enormous, terminal operators of its own.
So, you think we should FORCE US companies to bid on something they don't want to bid on? Or are you in favor of us "nationalizing" the ports a la Soviet Union?