The bottling up of Middle East oil is giving a lift to U.S. exports, but there are real limits on how much more they can grow. Why it matters: President Trump keeps talking up U.S. exports as the Strait of Hormuz is blocked, and oil and gas exports give America more geopolitical leverage. But at some point, the limits of its infrastructure — especially Gulf Coast ports and terminals — are likely to put a ceiling on how much more oil the U.S. can export. And nearer term, higher U.S. shipments can only offset a small amount of the massive drop in Middle East transit. The big picture: The Iran war could redraw the world's oil map, or at least parts of it. Think Mideast producers building pipelines to avoid the Strait of Hormuz, but also more tanker shipments from the U.S. and other countries outside the Persian Gulf.…