ho chi minh city vietnam u.s. president barack obama seek wednesday ease grow asian worry raucous election campaign succeed dominate incendiary rhetoric mogul donald trump republican party nominee think people sometimes look election system say mess obama tell townhall meet young leaders vietnam ho chi minh city formerly saigon usually end okay american people good people ... sometimes politics express goodness people say without refer specifically presidential candidates obama make comment end three-day trip vietnam whose high point announcement washington ban sales lethal weapons country vestige vietnam war would completely lift obama repeatedly insist lift embargo response beijing assertiveness south china sea critics accuse washington throw away powerful lever press communist-ruled vietnam improvements human right white house officials say arm move natural step take country enemy key part obama strategic rebalance towards asia important trade partner economy grow apace obama also announce peace corps would begin operate vietnam first time across asia policymakers startle trump isolationist foreign policy pronouncements challenge much status quo washington relations region many fear trump fee insecurity nations worry china grow power embolden nationalists authoritarians unravel obama pivot asia-pacific townhall ho chi minh city young woman exchange student montana ask obama think prospect trump democratic contenders hillary clinton bernie sanders follow white house usually eventually voters make good decisions democracy work reply obama whose criticism trump sharpen since clinch republican nomination things go ok. promise thousands people line streets ho chi minh city second day cheer enthusiastically wave mini-flags vietnam unite state obama drive way airport flight japan freewheel townhall greet stand ovation obama note two-thirds country population bear 1975 war end north vietnamese tank roll saigon bring u.s.-backed south vietnam communist rule obama prod vietnam leaders political freedoms visit critics government prevent meet woman rapper townhall ask support arts culture segue appeal people allow express however unusually long one-country visit warm mostly strengthen diplomatic economic relations annual u.s.-vietnam trade swell 450 million tie normalize 1995 45 billion last year washington big buyer vietnam televisions smartphones clothe seafood obama repeatedly tout benefit trans-pacific partnership tpp trade pact export-led vietnam one big beneficiaries survive opponents washington concern competition loss u.s. job also talk challenge climate change ask drying-up mekong river rice-bowl delta southern vietnam urge southeast asian countries work together mekong river sustain 60 million livelihoods flow laos thailand cambodia vietnam threat least 39 hydro-electric dam build development upstream vietnam china low river level allow seawater penetrate inland ruin vast swathe cropland fertile delta obama name upstream countries say unite state would provide small member state association southeast asian nations asean technical assistance evaluations need do hopefully ... information use negotiate international level try prevent project might bad effect say one things see asean small countries band together unit power magnify japan final stop obama swing asia attend summit group seven industrialize nations start thursday obama asians worry u.s. election 's go ok