I'm blaming Trump for continuing and amplifying the policy's negative effects. Hundreds of families have been separated by border enforcement without any records[1]. Children are being taken from their mothers and fathers and forcibly adopted via agencies run by white evangelical churches[2]. You're trying to deflect from the actual, unprecedented harm being caused now to people on the border by pointing at history.
Even the fact underlying your basic premise is wrong: Republicans had the majority in both houses of congress in January 3, 2015[3], gaining the Senate after having held the House since January 3, 2011. They continued to hold both in majority until the past midterm elections seated a Democratic house majority this January.
1. https://www.vox.com/2019/2/21/18234767/parents-separated-chi...
2. https://newrepublic.com/article/149161/uncertain-fate-migran...